Human Powered Sub team takes second place at International Submarine Races
Preparation and an accelerated design cycle were key in delivering Virginia Tech’s fastest vessel since 2003.
Virginia Tech’s Human Powered Submarine team (HPS) brought home second place at the 18th International Submarine Races. Their current vessel, EXLIENNI, posted Virginia Tech’s fastest speed at the competition since 2003.
Hosted every other year by the Naval Surface Warfare Center, Carderock Division, the International Submarine Races serve as a unique naval engineering competition that develops critical domestic scientific engineering talent.
The team
Since 1991, the HPS undergraduate engineering design team has designed, built, and raced submarines propelled and controlled entirely by a human pilot. The team is composed of more than 50 undergraduates from across the College of Engineering, who get hands-on learning in hydrodynamics, electronics, composite materials, physics, and machining.
Their current vessel, EXLIENNI — a nod to the “Enter Sandman” lyric “Exit light, enter night” — is a 12-foot, single-propeller submarine that is operated by a single pilot with four support divers.
The design cycle
To prepare for the biennial competition, HPS’s design process typically starts with a design year to plan out major systems, followed by a build year. Operating out of the Ware Lab, the subteams of hydrodynamics, electronics, controls, and structures focus on optimizing the vehicle’s speed, mechanical reliability, pilot safety, and comfort.
At their last ISR outing in 2023, however, HPS experienced setbacks on site and spent part of the week troubleshooting, which left limited time for runs in the basin. Acknowledging that they weren’t as prepared as they could have been, HPS leadership took a look at refining their timeline for the 2025 competition.
“We still operate on a two-year design cycle, but we’re shifting towards using both years as build years,” said Charlie Giglio, HPS head of design and a senior majoring in materials science and engineering. “Historically, we had a research-focused year followed by a build year. Now, we're starting hull manufacturing earlier, which gives us a head start — especially since everything begins with the hull. Once that's completed and joined, we can begin installing our systems, which is a time-intensive process.”
EXLIENNI’s predecessor vehicle, Kraken, had a smaller hull that limited pilot movement during operation. The team expanded the size of EXLIENNI’s hull to give more students opportunities to pilot, and to make room for a larger electronics canister, allowing for the electronics subteam to experiment with new systems. The team also made improvements to the design of the hatch door, an Achilles heel for Kraken, as it would periodically pop open and add significant drag.
Another major goal was to significantly increase the team's testing capacity.
“We dedicated the entire spring semester to testing, which hadn’t been done before,” said Maggie Campbell, HPS vice president and a senior majoring in ocean engineering. “In the past, we might conduct one or two pool tests and a quarry test before competition. This past cycle, we ran five pool tests, starting as early as February, and conducted an additional quarry test for added field experience.”
Off to the races
In late June, 17 high school and university teams from across the country faced off in the David Taylor Model Basin at Naval Surface Warfare Center Carderock. Subs are judged on various categories including design, innovation, and speed. Teams also submitted a design report and made a presentation to the judges during the week.
The race consists of a 100-meter drag course with a 10-meter timing gate. Officials record each sub’s speed over the full 100 meters and also over 10 meters in the middle, scoring whichever is faster. There’s no set number of runs a team can attempt. Teams can race as often as they can get in the queue.
HPS team members arrived on Sunday and quickly completed their dry test to ensure all submarine safety systems were in place. The Virginia Tech divers also finished their safety checkout dives that day, and then EXLIENNI passed the wet check, proving the team could safely load and remove a pilot underwater. By Monday morning, HPS was the first submarine in the water, the first in the queue, and the first to cross the finish line.
“This was a huge accomplishment for us,” said Nicole Quiram, HPS president and a senior majoring in industrial and systems engineering. “There were a few alumni in attendance who shed a tear at seeing how much we improved from the last competition and how strongly we opened this summer’s event.”
Thanks to their preparation, HPS was able to repeatedly get back in the queue all week long, sometimes racing as often as every 30 minutes. The results spoke for themselves. By the end of the week, Virginia Tech successfully crossed the finish line 17 times and placed second overall. EXLIENNI now holds the distinction of being Virginia Tech’s fastest submarine since 2003.
Prepping for 2027
EXLIENNI will serve as a training sub for new team members and a testbed for the development of new systems. Looking ahead, HPS is currently evaluating and assessing performance data to guide upcoming improvements. The team is also looking into attending the European International Submarine races in the future.
“This fall, we’re focusing on system analysis — what worked and what didn’t,” said Quiram. “Next semester, we’ll begin hull manufacturing and prototyping. Then in fall 2026, we’ll focus on integrating all the internal systems, with spring 2027 dedicated entirely to testing and refinement.”
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